Asymptomatic carotid artery stenosis may be treated with carotid endarterectomy (CEA), carotid artery stenting (CAS) or with best medical treatment (BMT) only. Definitive and evidence-based treatment recommendations for one of these options are currently not possible. Studies showing an advantage of CEA over BMT alone do not meet current standards from a pharmacological point of view. On the other hand, more recent data point to a further stroke risk reduction using BMT according to current standards. Studies on carotid artery stenting as a third alternative treatment are partially insufficient, especially when comparing CAS with BMT. Initiated in 2009, the randomized, controlled, multicenter SPACE-2 trial is intended to answer the question about the best treatment option of asymptomatic carotid artery stenosis; however, to increase recruitment rates as a condition for the successful completion of this important study, the trial design had to be modified.